Stable liquid enzyme compositions and methods of use in contact lens cleaning and disinfecting systems

ABSTRACT

Compositions containing a stable, liquid, ophthalmically acceptable enzyme and methods involving the combined use of these compositions with a polymeric antimicrobial agent, and complexing agent are disclosed for the simultaneous cleaning and disinfecting of contact lens. Methods for a daily use regimen are also disclosed.

BACKGROUND OF THE INVENTION

The present invention relates to the field of contact lens cleaning and disinfecting. In particular, this invention relates to liquid enzyme compositions and methods for cleaning human-worn contact lenses with those compositions. The invention also relates to methods of simultaneously cleaning and disinfecting contact lenses by combining the liquid enzyme compositions of the present invention with a chemical disinfecting agent.

Various compositions and methods for cleaning contact lenses have been described in the patent and scientific literature. Some of these methods have employed compositions containing surfactants or enzymes to facilitate the cleaning of lenses. The first discussion of the use of proteolytic enzymes to clean contact lenses was in an article by Lo, et al. in the Journal of The American Optometric Association, volume 40, pages 1106-1109 (1969). Methods of removing protein deposits from contact lenses by means of proteolytic enzymes have been described in many publications since the initial article by Lo, et al., including U.S. Pat. No. 3,910,296 (Karageozian, et al.).

Numerous compositions and methods for disinfecting contact lenses have also been described. Those methods may be generally characterized as involving the use of heat and/or chemical agents. Representative chemical agents for this purpose include organic antimicrobials such as benzalkonium chloride and chlorhexidine, and inorganic antimicrobials such as hydrogen peroxide and peroxide-generating compounds. U.S. Pat. Nos. 4,407,791 and 4,525,346 (Stark) describe the use of polymeric quaternary ammonium compounds to disinfect contact lenses and to preserve contact lens care products. U.S. Pat. Nos. 4,758,595 and 4,836,986 (Ogunbiyi) describe the use of polymeric biguanides for the same purpose.

Various methods for cleaning and disinfecting contact lenses at the same time have been proposed. Such methods are described in U.S. Pat. Nos. 3,873,696 (Randeri, et al.) and 4,414,127 (Fu), for example. A representative method of simultaneously cleaning and disinfecting contact lenses involving the use of proteolytic enzymes to remove protein deposits and a chemical disinfectant (monomeric quaternary ammonium compounds) is described in Japanese Patent Publication 57-24526 (Boghosian, et al.). The combined use of a biguanide (i.e., chlorhexidine) and enzymes to simultaneously dean and disinfect contact lenses is described in Canadian Patent No. 1,150,907 (Ludwig). Methods involving the combined use of dissolved proteolytic enzymes to clean and heat to disinfect are described in U.S. Pat. No. 4,614,549 (Ogunbiyi). The combined use of proteolytic enzymes and polymeric biguanides or polymeric quaternary ammonium compounds is described in copending, and commonly assigned U.S. patent application Ser. No. 08/156,043 and in corresponding European Patent Application Publication No. 0 456 467 A2.

The commercial viability of prior enzyme/disinfectant combinations has depended on the use of a stable enzyme tablet. More specifically, the use of solid enzymatic cleaning compositions has been necessary to ensure stability of the enzymes prior to use. In order to use such compositions, a separate packet containing a tablet must be opened, the tablet must be placed in a separate vial containing a solution, and the tablet must be dissolved in order to release the enzyme into the solution. This practice is usually performed only once a week due to the cumbersome and tedious procedure and potential for irritation and toxicity. Moreover, the enzymatic cleaning tablets contain a large amount of excipients, such as effervescent agents (e.g., bicarbonate) and bulking agents (e.g., compressible sugar). As explained below, such excipients can adversely affect both cleaning and disinfection of the contact lenses.

There have been prior attempts to use liquid enzyme compositions to clean contact lenses. However, those attempts have been hampered by the fact that aqueous liquid enzyme compositions are inherently unstable. When a proteolytic enzyme is placed in an aqueous solution for an extended period (i.e., several months or more), the enzyme may lose all or a substantial portion of its proteolytic activity. Steps can be taken to stabilize the compositions, but the use of stabilizing agents may have an adverse effect on the activity of the enzyme. For example, stabilizing agents can protect enzymes from chemical instability problems during storage in an aqueous liquid, by placing the enzymes in a dormant physical conformation. This conformation is referred to herein as being "partially denatured." However, such agents may also inhibit the ability of the enzymes to become active again (i.e., become "renatured") at the time of use. Finally, in addition to the general problems referred to above, a commercially viable liquid enzyme preparation for treating contact lenses must be relatively nontoxic, and must be compatible with other chemical agents used in treating contact lenses, particularly antimicrobial agents utilized to disinfect the lenses.

The following patents may be referred to for further background concerning prior attempts to stabilize liquid enzyme formulations: U.S. Pat. Nos. 4,462,922 (Boskamp); 4,537,706 (Severson); and 5,089,163 (Aronson). These patents describe detergent compositions containing enzymes. The detergent compositions may be used to treat laundry, as well as other industrial uses. Such detergents are not appropriate for treating contact lenses. The compositions of the present invention do not contain a detergent, or other agents potentially damaging or irritating to the eye.

U.S. Pat. No. 5,281,277 (Nakagawa) and Japanese Kokai Patent Applications Nos. 92-370197; 92-143718; and 92-24325 describe liquid enzyme compositions for treating contact lenses. The compositions of the present invention are believed to provide significant improvements relative to the compositions described in those publications.

SUMMARY OF THE INVENTION

The present invention is based in part on the finding that particular liquid enzyme compositions possess stability, preservative efficacy, and, when used in conjunction with a physiologically compatible, disinfecting solution, provide a good comfort and safety profile. Thus, the present invention has overcome issues of toxicity and efficacy to provide a more effective, yet physiologically delicate, system for cleaning contact lenses.

The compositions and methods of the present invention provide greater ease of use, and therefore, greater user compliance. This ease of use enables contact lens users to clean their lenses 2 to 3 times a week, or more preferably, every day. It has been found that daily use of the liquid enzyme compositions of the present invention results in dramatically better cleaning and safety, as compared to the once-a-week enzyme cleaning regimens currently being utilized.

The liquid enzyme compositions of the present invention contain critical amounts of selected stabilizing agents. The stabilizing agents utilized are combinations of a borate compound and one or more 2-3 carbon polyols. The amounts of stabilizing agents utilized have been delicately balanced, such that maximum stability is achieved, while maximum activity is later obtained when the composition is put into use. Furthermore, the borate compound also preserves the liquid enzyme compositions of the present invention from microbial contamination when the compositions are packaged in multiple use containers.

The present invention also provides methods for cleaning contact lenses with the above described liquid enzyme compositions. In order to clean a soiled lens, the lens is placed in a few milliliters of an aqueous solution and a small amount, generally one to two drops, of the enzyme composition is added to the solution. The lens is then soaked in the resultant cleaning solution for a time sufficient to clean the lens.

The liquid enzyme compositions of the present invention are preferably combined with an aqueous disinfecting solution to simultaneously clean and disinfect contact lenses. As will be appreciated by those skilled in the art, the disinfecting solution must be formulated so as to be compatible with contact lenses and ophthalmic tissues. The pH and osmolality or tonicity of the disinfecting solutions are particularly important. The solutions must have a pH of approximately 7.0 and a tonicity ranging from hypotonic to isotonic. The antimicrobial activity of many chemical disinfecting agents is adversely effected by ionic solutes (e.g., sodium chloride). Accordingly, the use of hypotonic solutions, that is, solutions having a relatively low concentration of ionic solutes, is generally preferred. Significantly, the use of the above described compositions has only a minor impact on the ionic strength of the disinfecting solution, and thus little to no effect on the antimicrobial efficacy of the disinfecting solution. As used in the methods of the present invention, 1 drop of the above described liquid enzyme compositions contributes only about 40 milliOsmoles per kilogram (mOs/kg) when added to about 5 mL of disinfecting solution, while prior enzyme tablet compositions contribute 100 to 200 or more mOs/kg to the same solution, due to the excipients needed to promote effervescing dissolution of the tablet or to add bulk.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a histogram detailing the effects of a liquid enzyme composition of the present invention on Type III and Type IV lens deposits, when used daily during a 135 day clinical study; FIG. 2 illustrates the frequency and reasons for lens replacements during that study; and FIG. 3 illustrates the efficacy of the liquid enzyme compositions of the present invention relative to prior enzyme cleaner compositions, based on the incidence of the frequency of significant slit-lamp findings during the clinical study.

DETAILED DESCRIPTION OF THE INVENTION

While Applicants do not wish to be bound by any theory, it is believed that the stability of these enzymes is enhanced by partially denaturing the proteins. The enzymes are partically denatured by forming a complex with the stabilizing agents. The enzymes are denatured to a point where the enzymes are inactivated, but where renaturation is easily achieved by dilution of the denatured enzyme/stabilizing agent complex in an aqueous medium. It is believed that the stabilizing agents compete with water for hydrogen bonding sites on the proteins. Thus, a certain percentage of these agents will effectively displace a certain percentage of water molecules. As a result, the proteins will change conformation (partially denature) to an inactive and complexed (with the stabilizing agents) form. When the enzyme is in an inactive form, it is prevented from self-degradation and other spontaneous, chemically irreversible events. On the other hand, displacement of too many water molecules results in protein conformational changes that are irreversible. In order to obtain a stable liquid enzyme composition of significant shelf life and thus commercial viability, a delicate balance point of maximum stability and maximum reversible renaturation must be ascertained. Such a point has now been discovered.

It has been found that the use of a polyol in combination with a borate compound achieves the stability and sustainable activity required in the liquid enzyme compositions of the present invention. The polyols utilized in the present invention are 2-3 carbon polyols. The most preferred borate is sodium borate. As used herein, the term "2-3 carbon polyol" refers to a compound with 2 to 3 carbon atoms and at least two hydroxy groups. Examples of 2-3 carbon polyols are glycerol, 1,2-propylene glycol, 1,3-propylene glycol and ethylene glycol. Examples of borate compounds are alkali metal salts of borate, boric acid and borax. As mentioned above, the borate compound also contributes to the anti-microbial preservation of the liquid enzyme compositions of the present invention to a level effective for multi-use dispensing.

Furthermore, it has been found that certain amounts of a 2-3 carbon polyol and a borate compound are critical for obtaining the stability and sustainable activity required in the liquid enzyme compositions of the present invention. It has been discovered that the combination of 50-70% to weight/volume ("% w/v") of a 2-3 carbon polyol and 4-8% w/v of a borate compound is required to achieve the necessary criteria for efficacious and commercially viable liquid enzyme compositions, as described above. The combination of about 50% w/v of a 2-3 carbon polyol and about 7.6% w/v sodium borate is most preferred. Examples 1, 2 and 3 below, further illustrate appropriate and inappropriate concentrations of these stabilizing agents. While any of the 2-3 carbon polyols can be components of the compositions of the present invention, particular polyols may be used depending on the particular intended use. For example, propylene glycol, which has preservative activity, is a preferred 2-3 carbon polyol when the need for a additional preservative present in a liquid enzyme composition of the present invention is desired.

The enzymes which may be utilized in the compositions and methods of the present invention include all enzymes which: (1) are useful in removing deposits from contact lenses; (2) cause, at most, only minor ocular irritation in the event a small amount of enzyme contacts the eye as a result of inadequate rinsing of a contact lens; (3) are relatively chemically stable and effective in the presence of the antimicrobial agents described below; and (4) do not adversely affect the physical or chemical properties of the lens being treated. For purposes of the present specification, enzymes which satisfy the foregoing requirements are referred to as being "ophthalmically acceptable."

The proteolytic enzymes used herein must have at least a partial capability to hydrolyze peptide-amide bonds in order to reduce the proteinaceous material found in lens deposits to smaller water-soluble subunits. Typically, such enzymes will exhibit some lipolytic, amylolytic or related activities associated with the proteolytic activity and may be neutral, acidic or alkaline. In addition, separate lipases or carbohydrases may be used in combination with the proteolytic enzymes, as well as thermally stable proteases.

Examples of suitable proteolytic enzymes include but are not limited to pancreatin, trypsin, subtilisin, collagenase, keratinase, carboxylase, papain, bromelain, aminopeptidase, Aspergillo peptidase, pronase E (from S. griseus) and dispase (from Bacillus polymyxa) and mixtures thereof. If papain is used, a reducing agent, such as n-acetylcysteine, may be required.

Microbial derived enzymes, such as those derived from Bacillus, Streptomyces, and Aspergillus microorganisms, represent a preferred type of enzyme which may be utilized in the present invention. Of this sub-group of enzymes, the most preferred are the Bacillus derived alkaline proteases generically called "subtilisin" enzymes.

The identification, separation and purification of enzymes is known in the art. Many identification and isolation techniques exist in the general scientific literature for the isolation of enzymes, including those enzymes having proteolytic and mixed proteolytic/amylolytic or proteolytic/lipolytic activity. The enzymes contemplated by this invention can be readily obtained by known techniques from plant, animal or microbial sources.

With the advent of recombinant DNA techniques, it is anticipated that new sources and types of stable proteolytic enzymes will become available. Such enzymes should be considered to fall within the scope of this invention so long as they meet the criteria for stability and activity set forth herein.

Pancreatin, subtilisin and trypsin are the most preferred enzymes for use in the present invention. Pancreatin is extracted from mammalian pancreas, and is commercially available from various sources, including Scientific Protein Laboratories (Waunakee, Wis., U.S.A.), Novo Industries (Bagsvaerd, Denmark), Sigma Chemical Co. (St. Louis, Mo., U.S.A.), and Boehringer Mannheim (Indianapolis, Ind., U.S.A.). Pancreatin USP is a mixture of proteases, lipases and amylases, and is defined by the United States Pharmacopeia ("USP"), as containing 1 USP unit each for proteases, lipases and amylases, respectively. The most preferred form of pancreatin is Pancreatin 9X. As utilized herein, the term "Pancreatin 9X" means a filtered (0.2 μm) pancreatin containing nine times the USP protease unit content. Subtilisin is derived from Bacillus bacteria and is commercially available from various commercial sources including Novo Industries (Bagsvaerd, Denmark), Fluka Biochemika (Buchs, Germany and Boehringer Mannheim. Trypsin is purified from various animal sources and is commercially available from Sigma Chemical Co. and Boehringer Mannheim.

The amount of enzyme used in the liquid enzyme compositions of the present invention will range from about 0.05 to 5% w/v, due to various factors, such as purity, specificity and efficacy. The preferred compositions of the present invention will contain pancreatin in the range of about 1 to 2% w/v; subtilisin in a range of about 0.01 to 0.3% w/v; or trypsin in the range of 0.1 to 0.7% w/v.

The cleaning methods of the present invention involve the use of an amount of enzyme effective to remove substantially or to reduce significantly deposits of proteins, lipids, mucopolysaccharides and other materials typically found on human-worn contact lenses. For purposes of the present specification, such an amount is referred to as "an amount effective to clean the lens." The amount of liquid enzyme cleaning composition utilized in particular embodiments of the present invention may vary, depending on various factors, such as the purity of the enzyme utilized, the proposed duration of exposure of lenses to the compositions, the nature of the lens care regimen (e.g., the frequency of lens disinfection and cleaning), the type of lens being treated, and the use of adjunctive cleaning agents (e.g., surfactants). For example, the methods of the present invention may generally employ an amount of the above-described liquid enzyme compositions sufficient to provide a final concentration of less than or equal to about 17 proteolytic activity units per milliliter (mL) of solution, preferably less than about 11 proteolytic activity units per mL, and most preferably less than about 5 proteolytic activity units per mL, following dispersion of the liquid enzyme compositions in a disinfecting solution or other aqueous solvents. For purposes of this specification, a "proteolytic activity unit" is defined as the amount of enzyme activity necessary to generate one microgram (meg) of tyrosine per minute (mcg Tyr/min), as determined by the casein-digestion, colorimetric assay described below.

Casein-Digestion Assay

A 5.0 mL portion of casein substrate (0.65% casein w/v) is equilibrated for 10 minutes (min)±5 seconds (sec) at 37° C. A 1.0 mL portion of enzyme solution (0.2 mg/ml) is then added to the casein substrate and the mixture vortexed, then incubated for 10 min±5 sec at 37° C. After incubation, 5.0 ml of 14% trichloroacetic acid is added and the resultant mixture immediately vortexed. The mixture is incubated for at least another 30 min, then vortexed and centrifuged for 15-20 min (approx. 2000 rpm). The supernatant of the centrifuged sample is filtered into a serum filter sampler and a 2.0 ml aliquot removed. To the 2.0 ml sample is added 5.0 ml of 5.3% Na₂ CO₃. The sample is vortexed, 1.0 ml of 0.67 N Folin's Phenol reagent is added, and the sample is immediately vortexed again, then incubated for 30 min at 37° C. The sample is then read on a visible light spectrophotometer at 660 nanometers (nm) versus purified water as the reference. The sample concentration is then determined by comparison to a tyrosine standard curve.

The liquid enzyme compositions of the present invention must be formulated to provide storage stability and antimicrobial preservation suitable for multiple use dispensing, and must provide effective enzymatic activity to breakdown and hence remove proteinaceous, sebaceous, and other foreign deposits on the contact lens. The liquid enzyme compositions must not contribute to the adverse effects of deposit formation on the lens, ocular irritation, or immunogenicity from continuous use. Additionally, when combined with a disinfecting solution containing an antimicrobial agent which is adversely affected by high ionic strength such as polyquaternium-1, the compositions of the present invention must have little or no impact on the ionic strength of the disinfecting solution.

As used in the present specification, the term "low osmolality effect" is defined as an increase in osmolality of about 0-50 milliOsmoles/kg when 1 to 2 drops of the liquid enzyme composition is added to the diluent solution. Osmolality is an indirect measure of available H₂ O hydrogen bonding and ionic strength of a solution. It is convenient to utilize osmolality measurements to define acceptable tonicity ranges for disinfecting solutions. As indicated above, the antimicrobial activity of disinfecting agents, particularly polymeric quaternary ammonium compounds such as polyquaternium-1, is adversely affected by high concentrations of sodium chloride or other ionic solutions.

The ionic strength or tonicity of the cleaning and disinfecting solution of the present invention has been found to be an important factor. More specifically, polymeric ammonium compounds, and particularly those of Formula (I), below, lose antimicrobial activity when the concentration of ionic solutes in the disinfecting solution is increased. The use of solutions having low ionic strengths (i.e., low concentrations of ionic solutes such as sodium chloride) is therefore preferred. Such low ionic strengths generally correspond to osmolalities in the range of hypotonic to isotonic, and more preferably in the range of 150 to 350 milliOsmoles per kilogram (mOs/kg). A range of 200 to 300 mOs/kg being is particularly preferred and a tonicity of about 220 mOs/kg is most preferred.

The liquid enzyme composition of the present invention must demonstrate effective cleaning efficacy while exhibiting minimal, or more preferably, enhanced effects on the anti-microbial efficacy of the disinfecting solution to which it is combined. It has unexpectedly been discovered that the liquid enzyme compositions of the present invention enhance the antimicrobial activity of disinfecting solutions containing polyquaternium-1, a polymeric quaternary ammonium disinfecting agent. In addition, the antimicrobial activity of the enzyme and antimicrobial agent combination has surprisingly been found to become even more effective than the antimicrobial agent alone when lenses are treated for extended periods of approximately one hour to overnight, with four to eight hours preferred. Since, for the sake of convenience, contact lenses are typically soaked overnight in order to be cleaned with enzymes or disinfected with chemical agents, this finding has practical significance.

While Applicants do not wish to be bound by any theory, it is believed that the above described effects are due to the disruption or lysis of microbial membranes by the enzyme, and is further attributable to the negligible impact of the compositions on the ionic strength of the disinfecting solution. As described above, a range of ionic strength, expressed in osmolality units, is critical for the antimicrobial efficacy of polymeric disinfecting agents. While the liquid enzyme cleaning compositions of the present invention have a high osmolality, due to the high concentration of a 2-3 carbon polyol, only 1 to 2 drops (approximately 30-60 uL) of the compositions are added to 2-10 mL of a disinfecting solution. The addition of 1 drop of the compositions of the present invention to 5 mL of a disinfecting solution increases the osmolality by about 40 mOsm/kg. Furthermore, this contribution to osmolality is primarily non-ionic. Therefore, the contribution of the compositions to the final ionic strength and osmolality of the enzyme/disinfectant solution is minor and is considered negligible.

The methods of the present invention utilize a disinfecting solution containing an antimicrobial agent. Antimicrobial agents can be oxidative, such as hydrogen peroxide, or non-oxidative polymeric antimicrobial agents which derive their antimicrobial activity through a chemical or physicochemical interaction with the organisms. As used in the present specification, the term "polymeric antimicrobial agent" refers to any nitrogen-containing polymer or co-polymer which has antimicrobial activity. Preferred polymeric antimicrobial agents include: polymeric quaternary ammonium compounds, such as disclosed in U.S. Pat. Nos. 3,931,319 (Green, et al.), 4,026,945 (Green, et al.) and 4,615,882 (Stockel, et al.) and the biguanides, as described below. The entire contents of the foregoing publications are hereby incorporated in the present specification by reference. Other antimicrobial agents suitable in the methods of the present invention include: benzalkonium halides, and biguanides such as salts of alexidine, alexidine free base, salts of chlorhexidine, hexamethylene biguanides and their polymers. The polymeric antimicrobial agents used herein are preferably employed in the absence of mercury-containing compounds such as thimerosal. The salts of alexidine and chlorhexidine can be either organic or inorganic and are typically gluconates, nitrates, acetates, phosphates, sulphates, halides and the like.

Particularly preferred are polymeric quaternary ammonium compounds of the structure: ##STR1## wherein: R₁ and R₂ can be the same or different and are selected from: N⁺ (CH₂ CH₂ OH)₃ X⁻, N(CH₃)₂ or OH;

X is a pharmaceutically acceptable anion, preferably chloride; and

n=integer from 1 to 50.

The most preferred compounds of this structure is polyquaternium-1, which is also known Onamer M™ (registered trademark of Onyx Chemical Corporation) or as Polyquad® (registered trademark of Alcon Laboratories, Inc.). Polyquaternium-1 is a mixture of the above referenced compounds, wherein X is chloride and R₁, R₂ and n are as defined above.

The above-described antimicrobial agents are utilized in the methods of the present invention in an amount effective to eliminate substantially or to reduce significantly the number of viable microorganisms found on contact lenses, in accordance with the requirements of governmental regulatory agencies, such as the United States Food and Drug Administration. For purposes of the present specification, that amount is referred to as being "an amount effective to disinfect" or "an antimicrobial effective amount." The amount of antimicrobial agent employed will vary, depending on factors such as the type of lens care regimen in which the method is being utilized. For example, the use of an efficacious daily cleaner in the lens care regimen may substantially reduce the amount of material deposited on the lenses, including microorganisms, and thereby lessen the amount of antimicrobial agent required to disinfect the lenses. The type of lens being treated (e.g., "hard" versus "soft" lenses) may also be a factor. In general, a concentration in the range of about 0.000001% to about 0.01% by weight of one or more of the above-described antimicrobial agents will be employed. The most preferred concentration of the polymeric quaternary ammonium compounds of Formula (I) is about 0.001% by weight.

Oxidative disinifecting agents may also be employed in the methods of the present invention. Such oxidative disinfecting agents include various peroxides which yield active oxygen in solution. Preferred methods will employ hydrogen peroxide in the range of 0.3 to 3.0% to disinfect the lens. Methods utilizing an oxidative disinfecting system are described in U.S. Pat. No. Re. 32,672 (Huth, et al.) the entire contents of which, are hereby incorporated in the present specification by reference.

As will be appreciated by those skilled in the art, the disinfecting solutions utilized in the present invention may contain various components in addition to the above-described antimicrobial agents, such as suitable buffering agents, chelating and/or sequestering agents and tonicity adjusting agents. The disinfecting solutions may also contain surfactants.

The tonicity adjusting agents, which may be a component of the disinfecting solution and may optionally be incorporated into the liquid enzyme composition, are utilized to adjust the osmotic value of the final cleaning and disinfecting solution to more closely resemble that of human. Suitable tonicity adjusting agents include, but are not limited to, sodium and potassium chloride, dextrose, calcium and magnesium chloride, the buffering agents listed above are individually used in amounts ranging from about 0.01 to 2.5% (w/v) and preferably, from about 0.5 to about 1.5% (w/v).

Suitable surfactants can be either cationic, anionic, nonionic or amphoteric. Preferred surfactants are neutral or nonionic surfactants which may be present in amounts up to 5% (w/v). Examples of suitable surfactants include, but are not limited to, polyethylene glycol esters of fatty acids, polyoxypropylene ethers of C₁₂ -C₁₈ is alkanes and polyoxyethylene, polyoxypropylene block copolymers of ethylene diamine (i.e. poloxamine).

Examples of preferred chelating agents include ethylenediaminetetraacetic acid (EDTA) and its salts (e.g., disodium) which are normally employed in amounts from about 0.025 to about 2.0% (w/v).

The methods of the present invention will typically involve adding a small amount of a liquid enzyme composition of the present invention to about 2 to 10 mL of disinfecting solution, placing the soiled lens into the enzyme/disinfectant solution, and soaking the lens for a period of time effective to dean and disinfect the lens. The small amount of liquid enzyme composition can range due to various applications and the amount of disinfecting solution used, but generally it is about 1 to 2 drops. The soiled lens can be placed in the disinfecting solution either before or after the addition of the liquid enzyme composition. Optionally, the contact lenses are first rubbed with a non-enzymatic daily surfactant cleaner prior to immersion in the enzyme/disinfectant solution. The lens will typically be soaked overnight, but shorter or longer durations are contemplated by the methods of the present invention. A soaking time of 4 to 8 hours is preferred. The methods of the present invention allow the above-described regimen to be performed once per week, but more preferably, every day. The following examples are presented to illustrate further, various aspects of the present invention, but are not intended to limit the scope of the invention in any respect.

EXAMPLE 1

A specific liquid enzyme composition of the present invention, and a suitable disinfecting solution for use in combination with that composition, are described below:

A. Liquid Pancreatin Composition

The following liquid enzyme composition represents a preferred embodiment of the present invention:

    ______________________________________                                         Ingredient            amount                                                   ______________________________________                                         Pancreatin (9X)       1.7% (w/v)*                                              Sodium borate         7.62% (w/v)                                              Propylene glycol      50% (v/v)                                                Water                 QS                                                       Hydrochloric acid/sodium hydroxide                                                                   QS**                                                     ______________________________________                                          *corresponds to 1700 proteolytic activity units/mL plus a 30% excess (mcg      Tyrosine/min)                                                                  **corresponds to an amount to adjust the pH to 6.0                             Note:                                                                          (w/v) means weight/volume;                                                     (v/v) means volume/volume;                                                     and QS means quantity sufficient                                         

The above formulation was prepared by first sequentially mixing propylene glycol, purified water, hydrochloric acid and sodium borate together. The solution was polish filtered (1.2 μm filter) into a sterile receiving tank, and then sterile filtered (0.2 μm filter). The required amount of pancreatin was then dissolved in an appropriate amount of water mid the solution was polish filtered (0.6 μm filter). This enzyme solution was then sterile filtered (0.2 μm filter) into the sterile receiving tank containing the sterilized propylene glycol/sodium borate solution. While mixing, the contents of the receiving tank were then brought to volume with an appropriate amount of water. The optimal pH of the above formulation is in the range of 6-7; a pH of 6 is most preferred.

B. Disinfecting Solution

The following formulation represents a preferred disinfecting solution:

    ______________________________________                                         Ingredient       w/v(%)                                                        ______________________________________                                         Polyquaternium-1 0.001 + 10% excess                                            Sodium chloride  0.48                                                          Disodium Edetate 0.05                                                          Citric acid monohydrate                                                                         0.021                                                         Sodium citrate dihydrate                                                                        0.56                                                          Purified water   QS                                                            ______________________________________                                    

To prepare the above formulation, sodium citrate dihydrate, citric acid monohydrate, disodium edetate, sodium chloride and polyquaternium-1, in the relative concentrations indicated above, were mixed with purified water and the components allowed to dissolve by stirring with a mixer. Purified water was added to bring the solution to almost 100%. The pH was recorded at 6.3 and adjusted to 7.0 with NaOH. Purified water was added to bring the solution to 100%. The solution was stirred and a pH reading of 7.0 was taken. The solution was then filtered into sterile bottles and capped.

EXAMPLE 2

Preferred liquid subtilisin and liquid trypsin compositions of the present invention for use in combination with a suitable disinfecting solution, e.g. EXAMPLE 1B., are described below:

Liquid Subtilisin and Trypsin Compositions

    ______________________________________                                         Ingredient            amount                                                   ______________________________________                                         Subtilisin or trypsin 0.3% (w/v)                                               Sodium borate         7.62% (w/v)                                              Propylene glycol      50% (v/v)                                                Water                 QS                                                       Hydrochloric acid/sodium hydroxide                                                                   QS*                                                      ______________________________________                                          *corresponds to an amount to adjust the pH to 6.0                        

The above liquid subtilisin and trypsin compositions are made in the same manner as the liquid pancreatin composition, described in EXAMPLE 1.

EXAMPLE 3

A comparative study of the effects of varying amounts of borate and propylene glycol in liquid enzyme compositions was performed. Aliquots of the compositions were stored in a controlled temperature room (26.7°±2° C.). At 6 and 12 weeks, aliquots were assayed for enzyme activity by the the casein-digestion method described above. Activity levels were compared with initial levels and expressed as percent remaining activity. Data demonstrating the criticality of the amounts of sodium borate and propylene glycol used in liquid enzyme compositions of the present invention versus alternative percentage amounts, as a function of enzyme stability, is given in Table I below:

                  TABLE I                                                          ______________________________________                                         COMPARISON OF THE STABILITY OF ALTERNATIVE                                     LIQUID ENZYME COMPOSITIONS VERSUS                                              A COMPOSITION OF THE PRESENT INVENTION                                         Composition                                                                              1       2       3     4     5     6                                  ______________________________________                                         Pancreatin 9X                                                                            1.7     1.7     1.7   1.7   1.7   1.7                                % (w/v)                                                                        Boric Acid %                                                                             0.155   0.155   0.155 0.155 0.155 --                                 (w/v)                                                                          Sodium Borate                                                                            0.035   0.035   0.035 0.035 0.035 7.62                               % (w/v)                                                                        Purified Water                                                                           60      50      40    30    10    50                                 (qs)                                                                           Propylene 40      50      60    70    90    50                                 Glycol % (v/v)                                                                 Activity at                                                                              71.9    86.6    88.2  92.9  *     97.7                               6 weeks (% of                                                                  initial activity)                                                              Activity at                                                                              44      66      65    74    *     98.4                               12 weeks (% of                                                                 initial activity)                                                              ______________________________________                                          *Initial values showed low activity                                      

Composition 6 illustrates a preferred embodiment of the present invention. Compositions 2, 3 and 4 contain propylene glycol in an amount required by the present invention, but do not contain an amount of borate (sodium borate and boric acid) required by the present invention. Compositions 1 and 5 contain amounts of propylene glycol and borate outside the ranges required by the present invention. Activity measurements obtained for compositions 24, containing from 50-70% propylene glycol, showed that similar stability (86.6-92.9% at room temperature) was obtained after 6 weeks of incubation, while compositions 1 and 5, containing 40 or 90% proplyene glycol, were significantly less stable (71.9% and an undetectable level, respectively). Compositions 1-5, were less stable (71.9-92.9%) than composition 6 (97.9%) through 6 weeks of incubation. Moreover, composition 6 exhibited a greater duration of stability, 98.4% at 12 weeks, as compared to a range of 44-74% for compositions 1-5.

EXAMPLE 4

Data demonstrating the stability of the liquid enzyme composition of Example 1 at temperatures of typical storage was ascertained. Aliquots of the composition were stored in a controlled temperature room (26.7°±2° C., RT), or in a chamber held to 35° C. At the appointed time, aliquots were tested for enzyme activity by the the casein-digestion method described above. Activity levels were compared with initial levels and expressed as percent remaining activity. The results are presented in Table II below:

                  TABLE II                                                         ______________________________________                                         EFFECT OF STORAGE TIME ON A LIQUID ENZYME                                      COMPOSITION AT ROOM TEMPERATURE (RT)                                           AND AT 35° C.                                                                           % Remaining Activity                                           Time (Weeks)      RT     35° C.                                         ______________________________________                                         2                 94.4   83.0                                                  4                 94.0   76.5                                                  6                 97.7   81.1                                                  8                 99.0   80.2                                                  12                98.4   78.3                                                  ______________________________________                                    

The data presented in Table II confirm the stability of liquid enzyme compositions of the present invention. The data are based on a compilation of 4 separate lots and experiments. The data show virtually no deleterious effect on enzyme activity through 12 weeks at room temperature, the final measurement being 98.4%. The liquid enzyme composition of Example 1 was also effective in maintaining activity at the elevated temperature of 35° C. for 12 weeks, showing approximately a 20% loss in activity.

EXAMPLE 5

As indicated above, it has been found that one of the protease components of pancreatin, trypsin, is significantly more stable than one of the other protease components, chymotrypsin. This finding was confirmed by a study which compared the relative stability of liquid enzyme compositions containing 0.3% w/v of trypsin and chymotrypsin, respectively. The compositions were identical to the composition described in Example 1 above, except for the enzyme component Aliquots of the compositions were stored in a chamber maintained at 35° C. At the appointed time, aliquots were tested for enzyme activity by the casein-digestion method described above. Activity levels were compared with initial levels and expressed as percent remaining activity. The results of the study are presented in Table III below:

                  TABLE III                                                        ______________________________________                                         COMPARISON OF THE STABILITY OF LIQUID ENZYME                                   COMPOSITIONS CONTAINING TRYPSIN OR                                             CHYMOTRYPSIN STORED AT 35° C.                                                       % Remaining Activity                                               Time          Trypsin  Chymotrypsin                                            ______________________________________                                         24 hours      100      79.8                                                    1 weeks       100       7.3                                                    2 weeks       96.0     --                                                      3 weeks       93.2     *                                                       4 weeks       93.2     *                                                       ______________________________________                                          *no measurements taken after 2 week time point, when all activity was los                                                                               

The trypsin composition demonstrated an excellent stability profile at 35° C., in contrast with the chymotrypsin composition, an alternative composition not part of the present invention.

EXAMPLE 6

The disinfecting efficacy of the present invention was evaluated by determining the rate and extent of kill achieved with an aqueous system formed by combining the liquid enzyme composition and disinfecting solution described in EXAMPLE 1 above. That system was tested against six microorganisms: Staphylococcus epidermidis, Pseudomonas aeruginosa, Serratia marcescens, Candida albicans, Aspergillus fumigatus, and Herpes simplex. The test procedures and results are described below.

A 0.1 ml volume of inoculum (10⁸ colony forming units/mL) was first added to a 10 ml volume of the disinfecting solution of EXAMPLE 1, followed by the addition of 2 drops of the liquid enzyme composition of EXAMPLE 1. A similarly inoculated 10 ml volume of the disinfecting solution of EXAMPLE 1 was used as a control. The solutions were maintained at room temperature throughout the test. Each microorganism and test solution was tested individually. Sets of four replicate (n=8) samples were tested for each organism.

At selected time intervals of 0, 1, 2, 3, 4, 6, 8 and 24 hours (Herpes simplex, at 4 hours only), a 1 ml volume of the inoculated test solution was removed and appropriate serial dilutions were made in sterile 0.9% sodium chloride solution dilution blanks. Pour-plates were prepared with soybean-casein digest agar containing 0.07% Asolectin and 0.5% Polysorbate 80. At Time 0, a 1.0 ml volume of the saline control was removed and serial dilution pour-plates were prepared using the same recovery medium and dilution blanks. The Time 0 saline control count was used as the initial count. The pour-plates were incubated at 30°-35° C. for appropriate incubation periods. The number of surviving organisms at each time interval was then determined. The results are summarized in Tables IV-IX below.

                  TABLE IV                                                         ______________________________________                                         ANTIMICROBIAL ACTIVITY; S. EPIDERMIDIS                                                                      LOG                                               SAMPLE            TIME (HR)  REDUCTION                                         ______________________________________                                         Liquid pancreatin composition                                                                    1          2.7 ± 0.2                                      and disinfecting solution of                                                                     2          3.3 ± 0.1                                      EXAMPLE 1         3          3.6 ± 0.2                                                        4          4.2 ± 0.2                                                        6          4.8 ± 0.2                                                        8          4.9 ± 0.1                                                        24         4.8 ± 0.1                                      Control (disinfecting solution of                                                                1          2.2 ± 0.1                                      EXAMPLE 1)        2          2.7 ± 0.1                                                        3          3.1 ± 0.1                                                        4          3.3 ± 0.1                                                        6          3.7 ± 0.1                                                        8          4.1 ± 0.3                                                        24         4.9 ± 01                                       ______________________________________                                    

                  TABLE V                                                          ______________________________________                                         ANTIMICROBIAL ACTIVITY: P. AERUGINOSA                                                                       LOG                                               SAMPLE            TIME (HR)  REDUCTION                                         ______________________________________                                         Liquid pancreatin composition                                                                    1          0.8 ± 0.1                                      and disinfecting solution of                                                                     2          1.2 ± 0.1                                      EXAMPLE 1         3          1.5 ± 0.1                                                        4          1.9 ± 0.1                                                        6          2.6 ± 0.1                                                        8          3.0 ± 0.1                                                        24         4.8 ± 0.6                                      Control (disinfecting solution of                                                                1          0.1 ± 0.1                                      EXAMPLE 1)        2          0.4 ± 0.1                                                        3          0.6 ± 0.1                                                        4          0.9 ± 0.1                                                        6          1.1 ± 0.1                                                        8          1.4 ± 0.1                                                        24         3.3 ± 0.1                                      ______________________________________                                    

                  TABLE VI                                                         ______________________________________                                         ANTIMICROBIAL ACTIVITY: S MARCESCENS                                                                        LOG                                               SAMPLE            TIME (HR)  REDUCTION                                         ______________________________________                                         Liquid pancreatin composition                                                                    1          0.1 ± 0.1                                      and disinfecting solution of                                                                     2          1.2 ± 0.1                                      EXAMPLE 1         3          1.5 ± 0.1                                                        4          1.9 ± 0.0                                                        6          2.6 ± 0.0                                                        8          3.0 ± 0.1                                                        24         4.8 ± 0.6                                      Control (disinfecting solution of                                                                1          0.1 ± 0.1                                      EXAMPLE 1)        2          0.4 ± 0.1                                                        3          0.6 ± 0.0                                                        4          0.9 ± 0.0                                                        6          1.1 ± 0.0                                                        8          1.4 ± 0.1                                                        24         3.3 ± 0.1                                      ______________________________________                                    

                  TABLE VII                                                        ______________________________________                                         ANTIMICROBIAL ACTIVITY: C. ALBICANS                                                                         LOG                                               SAMPLE            TIME (HR)  REDUCTION                                         ______________________________________                                         Liquid pancreatin composition                                                                    1          0.1 ± 0.1                                      and disinfecting solution of                                                                     2          0.1 ± 0.1                                      EXAMPLE 1         3          0.1 ± 0.1                                                        4          0.1 ± 0.0                                                        6          0.1 ± 0.0                                                        8          0.2 ± 0.1                                                        24         0.2 ± 0.0                                      Control (disinfecting solution of                                                                1          0.1 ± 0.1                                      EXAMPLE 1)        2          0.0 ± 0.1                                                        3          0.1 ± 0.0                                                        4          0.1 ± 0.0                                                        6          0.1 ± 0.0                                                        8          0.1 ± 0.1                                                        24         0.1 ± 0.1                                      ______________________________________                                    

                  TABLE VIII                                                       ______________________________________                                         ANTIMICROBIAL ACTIVITY: A. FUMIGATUS                                                                        LOG                                               SAMPLE            TIME (HR)  REDUCTION                                         ______________________________________                                         Liquid pancreatin composition                                                                    1          0.1 ± 0.1                                      and disinfecting solution of                                                                     2          0.1 ± 0.0                                      EXAMPLE 1         3          0.1 ± 0.0                                                        4          0.2 ± 0.1                                                        6          0.3 ± 0.1                                                        8          0.3 ± 0.1                                                        24         0.5 ± 0.1                                      Control (disinfecting solution of                                                                1          0.1 ± 0.1                                      EXAMPLE 1)        2          0.1 ± 0.1                                                        3          0.1 ± 0.0                                                        4          0.1 ± 0.1                                                        6          0.2 ± 0.1                                                        8          0.3 ± 0.1                                                        24         0.5 ± 0.1                                      ______________________________________                                    

                  TABLE IX                                                         ______________________________________                                         ANTIMICROBIAL ACTIVITY: HERPES SIMPLEX                                                                     LOG                                                SAMPLE           TIME (HR)  REDUCTION                                          ______________________________________                                         Liquid pancreatin composition                                                                   4          3.7 ± 0.4                                       and disinfecting solution of                                                   EXAMPLE 1                                                                      C (disinfecting solution of                                                                     4          0.3 ± 0.2                                       EXAMPLE 1                                                                      ______________________________________                                    

As illustrated in Tables IV-IX, the log reductions achieved with the liquid enzyme/disinfecting solution combination were generally greater than the log reductions achieved with the disinfecting solution control. This difference was statistically significant for S. epidermidis, P. aeruginosa, S. Marcescens and H. simplex (at 4 hours). A trend for a statistical difference was shown for A. fumigatus. The antimicrobial activity against C. albicans was equal.

EXAMPLE 7

The disinfecting efficacy of a composition of the present invention was evaluated by determining the rate and extent of kill achieved with an aqueous system formed by combining the liquid enzyme composition and disinfecting solution described in EXAMPLE 1 above, except that subtilisin in the amount of 0.1% w/v was substituted for pancreatin, in the liquid enzyme composition. That system was tested against Serratia marcescens. The test procedures were the same as EXAMPLE 6, except that antimicrobial activity was only evaluated at 4 and 24 hours. The test results, expressed as log reduction are presented in Table X below.

                  TABLE X                                                          ______________________________________                                         EFFECTS OF A SUBTILISIN CONTAINING LIQUID                                      ENZYME COMPOSITION ON THE ANTIMICROBIAL                                        ACTIVITY OF A POLYQUATERNIUM-1                                                 DISINFECTING SOLUTION                                                          LOG REDUCTION                                                                         Disinfecting Solution                                                                         Liquid Enzyme (subtilisin) +                             Time   Control        Disinfecting Solution                                    ______________________________________                                         4 hours                                                                               0.85 ± 0.07 1.33 ± 0.15                                           24 hours                                                                              3.65 ± 0.35 3.37 ± 1.01                                           ______________________________________                                    

As illustrated in Table X, the liquid enzyme composition containing subtilisin had an enhancing effect on the antimicrobial activity of the disinfecting solution of EXAMPLE 1, at 4 hours.

EXAMPLE 8

The following comparative example demonstrates the effectiveness of the liquid enzyme compositions of the present invention with different disinfecting agents. The effect of the liquid enzyme compositions of the present invention, in particular the liquid enzyme composition of EXAMPLE 1 (referred to below as "Liquid Enzyme" or "LE"), on the antimicrobial activity of a polyquaternium-1 multi-purpose solution (OPTI-ONE® Disinfecting Solution) and a polymeric biguanide multi-purpose solution (ReNu® Multi-Purpose Solution) is illustrated in Table XI below.

Two drops of Liquid Enzyme were added to 10 mL of the polyquaternium-1 and polymeric biguanide disinfecting solutions. The respective disinfecting solutions alone were also tested as controls. The protocol described in EXAMPLE 6 was followed, except that the experiments were terminated at a time point of 4 hours. Microbiological data, in the form of log reductions achieved against Staphylococcus epidermidis, Pseudomonas aeruginosa, Serratia marcescens, Candida albicans, and Aspergillus fumigatus, were ascertained. The results are presented in Table XI below.

                  TABLE XI                                                         ______________________________________                                         ANTIMICROBIAL ACTIVITY OF A POLYQUATERNIUM-1                                   MULTI-PURPOSE SOLUTION AND A POLYMERIC                                         BIGUANIDE MULTI-PURPOSE SOLUTION WITH                                          LIQUID ENZYME*                                                                         OPTI-                 ReNu ®                                                                             ReNu ®                                       ONE ®  OPTI-      polymeric                                                                              poly-                                            polyquater-                                                                               ONE ®  biguanide                                                                              meric                                            nium-1     polyquater-                                                                               multi-  biguanide                                        multi-purpose                                                                             nium-1     purpose multi-                                           solution + multi-purpose                                                                             solution +                                                                             purpose                                  Organism                                                                               LE**       solution   LE**    solution                                 ______________________________________                                         A.      0.1        0.1        0.1     0.2                                      fumigatus                                                                      C.      0.1        0.1        0.2     1.3                                      albicans                                                                       S.      2.4        2.4        1.1     3.2                                      marcescens                                                                     P.      3.5        3.5        3.3     4.0                                      aeruginosa                                                                     S.      4.6        4.0        1.8     2.3                                      epidermidis                                                                    ______________________________________                                          *disinfection time is 4 hours                                                  **LE = the liquid pancreatin composition of EXAMPLE 1                    

The results demonstrate no deleterious effects of Liquid Enzyme on the polyquaternium-1 disinfecting solution, and an enhancement of the Staphylococcus epidermidis kill after 4 hours. Conversely, the Liquid Enzyme composition had a reduced effect on the disinfecting efficacy of the polymeric biguanide disinfecting solution with respect to all five organisms tested. These results illustrate a preferred method of the present invention, in using a polyquaternium-1 disinfecting solution with liquid enzyme compositions of the present invention.

EXAMPLE 9

A 135 day study comparing the efficacy of the compositions and methods of the present invention, with other known compositions and methods was performed. Three different clinical observations were made: 1) frequency, of Type III and Type IV lens deposits (Rudko grading system); 2) frequency and reasons for lens replacement; and 3) frequency of significant slit-lamp findings. A "Type III" lens deposit is defined as a foreign deposit observable by a clinician's naked eye either before or after blotting with a tissue. A "Type IV" lens deposit is defined as a heavily deposited lens. A "slit lamp finding" is defined as an abnormality observed on the cornea, by a clinician using an optometrist's slit-lamp apparatus.

Three different cleaning formulations and their associated methods were compared with a method of the present invention ("LE"): 1) "Historical control"--a data set comprised of 5 different studies wherein the lens was cleaned daily with a surfactant cleaner followed by an 8 hour soaking in a disinfecting solution containing polyquaternium-1, combined with a once/week, 8 hour soaking of the lens in a polyquaternium-1 disinfecting solution containing a dissolved pancreatin tablet; 2) "Protocol 1"--a protocol utilizing a polyquaternium-1 disinfecting solution containing citrate wherein the lens is rubbed daily for several seconds with this solution and then soaked 8 hours in this solution, combined with a once/week, 8 hour soaking of the lens in a polyquaternium-1 disinfecting solution containing a dissolved pancreatin tablet; 3) "Protocol 2"--a protocol utilizing a polymeric biguanide disinfecting solution containing a surfactant, wherein the lens is rubbed daily for several seconds, then soaked in this solution for 8 hours, combined with a once/week soaking of the lens in this solution for 15 minutes to 2 hours, followed by removing the lens and placing it in a fresh polymeric biguanide solution containing a surfactant and a dissolved subtilisin enzyme tablet and soaking for 8 hours; and 4) "LE"--a method and composition of the present invention wherein the lens is rubbed daily with a surfactant cleaner, followed by an 8 hour soaking in a solution containing polyquaternium-1 and 2 drops of the liquid enzyme composition of EXAMPLE 1 ("Liquid Enzyme"). Table XII, below, provides a tabulated comparison of the compositions and protocols of this study.

                  TABLE XII                                                        ______________________________________                                         COMPARISON OF CLEANING AND DISINFECTING                                        COMPOSITIONS AND PROTOCOLS                                                     HISTOR-      PROTO-     PROTO-                                                 ICAL         COL 1      COL 2     LE                                           ______________________________________                                         CLEAN- Daily, with                                                                              Daily, with                                                                               Daily, with                                                                            Daily, with                                ING    a surfactant                                                                             OPTI-      ReNu ®                                                                             a surfactant                                      cleaner   ONE ®  polymeric                                                                              cleaner                                                     polyquater-                                                                               biguanide                                                           nium-1     solution                                                            solution                                                      DISIN- Daily (8  Daily (8   Daily (8                                                                               Daily (8                                   FECT-  hrs) with a                                                                              hrs) with  hrs) with                                                                              hrs) with                                  ING    polyquater-                                                                              OPTI-      ReNu ®                                                                             OPTI-                                             nium-1    FREE ® polymeric                                                                              FREE ®                                        solution  polyquater-                                                                               biguanide                                                                              polyquater-                                                 nium-1     solution                                                                               nium-1                                                      solution           solution                                   ENZY-  Weekly (8 Weekly (8  Weekly (8                                                                              Daily (8                                   MATIC  hrs) with hrs) with  hrs) with                                                                              hrs) with a                                CLEAN- a polyqua-                                                                               OPTI-      ReNu ®                                                                             OPTI-                                      ER     ternium-1 FREE ® polymeric                                                                              FREE ®                                        solution  polyquater-                                                                               biguanide                                                                              polyquater-                                       containing                                                                               nium-1     solution                                                                               nium-1                                            a dissolved                                                                              solution   containing                                                                             solution                                          pancreatin                                                                               containing a dissolved                                                                            containing                                        tablet    a dissolved                                                                               subtilisin                                                                             1 drop of                                                   pancreatin tablet  Liquid                                                      tablet             Enzyme                                     ______________________________________                                    

The results are presented graphically in FIGS. 1-3. The protocol including the liquid enzyme composition of the present invention ("LE"), demonstrated superior efficacy in maintaining lenses free of Type III and Type IV deposits, as compared to the other known methods and compositions. As shown ini FIG. 1, the present invention eliminated Type III and Type IV lens deposits (0.0% frequency) while the other protocols exhibited a 6.5-8.4% lens deposit frequency.

FIG. 2 further demonstrates the cleaning efficacy of the compositions and methods of the present invention. Lenses cleaned with the LE composition needed replacement, due to lens deposits, on a frequency of 0.3% as compared to a range of 1.4-8.5% for the other compositions and methods studied. The LE composition also demonstrated lower slit-lamp findings as compared to the three other compositions and methods (FIG. 3).

The invention in its broader aspects is not limited to the specific details shown and described above. Departures may be made from such details within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its advantages. 

What is claimed is:
 1. A liquid enzyme composition for cleaning contact lenses comprising:an enzyme in an amount effective to clean the lens; 50-70% v/v of propylene glycol; 4-8% w/v of a borate compound; and water, said composition having a pH of 6-7.
 2. The composition according to claim 1, wherein the enzyme is selected from the group consisting of: pancreatin, subtilisin and trypsin.
 3. The composition according to claim 1, wherein the borate compound is sodium borate in the mount of 6-8% w/v, or boric acid in the amount of 4-5.5% w/v.
 4. The composition according to claim 1, wherein the enzyme is selected from the group consisting of: pancreatin, subtilisin and trypsin; and the borate compound is sodium borate in the amount of 6-8% w/v, or boric acid in the amount of 4-5.5% w/v.
 5. The composition according to claim 1, wherein the composition has a pH of 6.0, the concentration of propylene glycol is 50% v/v; and the borate compound is sodium borate in the amount of 7.6% w/v.
 6. The composition according to claim 5, wherein the enzyme is selected from the group consisting of: pancreatin, subtilisin and trypsin.
 7. The composition according to claim 5, wherein the enzyme is pancreatin in the amount of 1.7% w/v.
 8. A method for cleaning and disinfecting a contact lens comprising:placing the lens in an aqueous disinfecting solution containing an amount of an antimicrobial agent effective to disinfect the lens; forming an aqueous disinfectant/enzyme solution by dispersing a small amount of a liquid enzyme cleaning composition in said disinfecting solution, said cleaning composition comprising: an enzyme in an amount effective to clean the lens, 50-70% v/v of propylene glycol, 4-8% w/v of a borate compound, and water; and soaking the lens in said aqueous disinfectant/enzyme solution for a period of time sufficient to clean and disinfect the lens.
 9. The method according to claim 8, wherein said cleaning composition has a pH of 6.0, the enzyme is pancreatin in the amount of 1.7% w/v, the concentration of propylene glycol is 50% v/v; and the borate compound is sodium borate in the amount of 7.6% w/v.
 10. The method according to claim 8, wherein the antimicrobial agent comprises 0.00001% to 0.05% w/v of polyquaternium-1.
 11. The method according to claim 9, wherein the antimicrobial agent comprises 0.00001% to 0.05% w/v of polyquaternium-1, and the disinfecting solution has a pH of 7.0.
 12. The method according to claim 8, wherein the disinfecting solution comprises:about 0.5% w/v of sodium chloride; about 0.05% w/v of disodium edetate; about 0.02% w/v of citric acid monohydrate; about 0.6% w/v of sodium citrate dihydrate; about 0.001% w/v of polyquaternium-1; and water, and has a pH of 7.0.
 13. The method according to claim 8, wherein the aqueous disinfecting solution has an osmolality of from 150 to 350 mOsmoles/kg.
 14. A method of cleaning a contact lens which comprises:forming an aqueous enzymatic cleaning solution by dispersing a small amount of a liquid enzyme composition in an aqueous solvent, said cleaning composition comprising an enzyme in an amount effective to clean the lens, 50-70% v/v of propylene glycol, 4-8% w/v of a borate compound, and water; and soaking the lens in the enzymatic cleaning solution for a period of time sufficient to clean the lens.
 15. A method according to claim 14, wherein the enzyme is selected from the group consisting of: pancreatin, subtilisin and trypsin.
 16. The method according to claim 14, wherein the borate compound is sodium borate in the amount of 6-8% w/v, or boric acid in the amount of 4-5.5% w/v.
 17. The method according to claim 14, wherein the enzyme is selected from the group consisting of: pancreatin, subtilisin and trypsin; and the borate compound is sodium borate in the amount of 6-8% w/v, or boric acid in the amount of 4-5.5% w/v.
 18. The method according to claim 14, wherein the composition has a pH of 6.0, the concentration of propylene glycol is 50% v/v; and the borate compound is sodium borate in the amount of 7.6% w/v.
 19. The method according to claim 18, wherein the enzyme is selected from the group consisting of: pancreatin, subtilisin and trypsin.
 20. The method according to claim 18, wherein the enzyme is pancreatin in the amount of 1.7% w/v.
 21. The composition according to claim 5, wherein the enzyme is trypsin in the amount of 0.3% w/v.
 22. The method according to claim 18, wherein the enzyme is trypsin in the amount of 0.3% w/v. 